The present invention relates to a device for treating the surface of plate-like articles, and more specifically to a device for treating the surfaces of semiconductor wafers (thin plates having circular flat planes).
In producing the semiconductor devices, the impurities or chemicals adhered on the semiconductor wafers must be washed away or foreign matters must be removed by way of etching prior to subjecting the semiconductor wafers to treatments such as photoetching, thermal oxidation and diffusion.
So far, the surface treatment for washing or etching the wafers has been performed using a surface treatment device in which a plurality of wafers are accommodated in a plurality of stages in a cartridge, and the cartridge is manually operated up and down or to and fro, such that the wafers are alternately plunged into of or taken out, a vessel containing surface treatment liquid such as washing solution or etching solution. With the device of this type, however, the wafers are subjected to different concentrations and temperatures of the surface treating liquid depending upon whether the wafers are located at the center or near the sides in the cartridge. Therefore, the surfaces are not uniformly treated, and the degree of surface treatment differs depending upon the individual wafers, causing defects to the semiconductor devices. Further, with the surface treatment by the abovementioned device, the chemicals and the washing liquid are not sufficiently stirred, giving rise to the occurrence of washing spots on the wafers and etching spots, losing uniformity and causing the quality to be degraded.
That is to say, with the surface treatment device of this type in which many wafers (for example, 25 pieces of wafers) are held by the cartridge and are subjected to the surface treatment such as washing or etching, the surfaces of the wafers tended to be nonuniformly treated depending upon the positions at which the wafers are located, or due to the stagnation of the treating liquid in the vessel, in the wafers or among the wafers. Further, when the surface treatment device of this type were to be automatically operated, the mechanism for moving the cartridge in the up and down directions or in the back and forth directions, and the handling mechanism tended to become bulky, making it difficult to continuously carry out the surface treatment.
Another conventional wafer washing system may be represented by a spinner system which sprays the washing liquid to the wafers. According to this system, the wafers can be continuously treated piece by, piece. However, since the back surface of the wafer was fastened by chuck to a rotary jig of the spinner, the back surface of the wafer was not washed; therefore, both surfaces of the wafer were not simultaneously washed.
Further, in continuously treating the surfaces of the wafers by successively etching the wafers using a variety of chemical liquids, it is essential to wash the wafers with pure water before and after the etching with chemical liquids. For this purpose, a path for conveying the wafers must be provided between the etching vessel and the washing vessel, and means for conveying the wafers must be provided among the etching vessel, washing vessel and the conveying path, causing the surface treatment device to become complex in construction, requiring increased areas as well as increased installation costs.
Moreover, according to a conventional drying device for drying the wafers of which the surfaces have been treated, the cartridge for accommodating the wafers is introduced into a drying chamber, and a clean gas (such as air or nitrogen gas) is blown from the nozzles in the chamber to dry the wafers. Therefore, the conventional drying device presented the following defects. Namely, (1) the cartridge has a plurality of V-shaped grooves for accommodating the wafers. However, the surface treatment liquid tends to stay in the V-shaped grooves. Therefore, large amounts of the water must be dried requiring extended periods of time. The extended drying time can further be attributed to the fact that wide treatment chamber is necessary for batch-wise treatment needing extended periods of time for removing the moisture filled in the chamber. (2) A large cartridge revolving in the treatment chamber creates air flow. This causes the scattered water droplets to be bounced by the wall of the treatment chamber. The water droplets fly again with the air flow to adhere onto the wafers. Therefore, the cleanliness becomes nonuniform among the wafers, causing the quality to be dispersed. (3) Since the batchwise treatment method is employed, the wafers are loaded or unloaded in the treatment chamber being accommodated in the cartridge of a large size. Further, in manipulating the device, attention must be given to that the wafers are not removed from the cartridge. To automatically perform the loading and unloading, therefore, complicated and large-scale mechanism will be necessary.